In fiber optic communications and other optical applications, optical switches are employed to selectively route optical signals. One type of prior art switch is the moving fiber switch, in which an input fiber is caused to mechanically move between two or more output fibers to allow an optical signal to be routed to a selected one of the output fibers. Another example is the electro-optic switch, which employs a material such as lithium nibate (LiNbO.sub.3) having an index of refraction which is a function of an applied electric field. Depending on the amplitude of an applied electric field, an input optical signal is routed along a different surface waveguide path to a selected output port. Another type of prior art switch is the glass waveguide thermo-optic switch. This switch employs a material having a temperature-dependent index or refraction. By applying electrical current to a metallized line or the like adjacent to the material to thereby produce a local temperature rise, an optical signal is selectively routed to a desired path.